Define aidl-cpp executable

This executable has a distinct usage which reflects that it generates
a very different sort of code.

Bug: 23599341
Test: unittests pass, added new Options unit test

Change-Id: I6750e7146949659a3af0246ad1bca0fa23afb2d5
diff --git a/main_java.cpp b/main_java.cpp
index 7c90145..9bd6768 100644
--- a/main_java.cpp
+++ b/main_java.cpp
@@ -33,7 +33,7 @@
 
   switch (options->task) {
     case JavaOptions::COMPILE_AIDL_TO_JAVA:
-      return android::aidl::compile_aidl(*options);
+      return android::aidl::compile_aidl_to_java(*options);
     case JavaOptions::PREPROCESS_AIDL:
       return android::aidl::preprocess_aidl(*options);
   }